FRANKFURT, March 20 (Reuters) - SAP, Europe's largest software maker, said on Friday it expected the weak euro boost to operating profit growth by up to 14 percentage points, upping its forecast after the currency weakened further in recent weeks.

The forecast, published in a U.S. securities filing, compares with a 1 percentage point currency boost which it forecast as recently as January. The euro has lost around a quarter of its value against the dollar since May.

A weak euro makes the German business software maker's products and services more competitive in markets outside Europe. It reports results in euros, but counts much of its sales and operating costs in dollars and other currencies.

Excluding currency effects, SAP said it still expected full-year operating profit to be between 5.6 to 5.9 billion euros ($6.03 billion-$6.36 billion), which means growth would be flat to up to 5 percent.

With the new currency guidance included, SAP would reach operating profit growth of 19 percent if it hit the top of its target range.

By contrast, SAP's U.S. rival Oracle said on Tuesday revenue for its latest quarter would have been 6 percent higher but for the strong dollar. In constant currency terms, revenue was flat year on year.

The euro hit a 12-year low under $1.05 this week, largely driven by the divergent policy paths of the U.S. Federal Reserve and European Central Bank.

SAP also said it expected the weaker euro to result in a 12 to 17 percentage point boost to both first quarter operating profit and revenue growth.

STMicroelectronics, Europe's largest chipmaker, was up 1.9 percent after an upgrade from Morgan Stanley, which said the weaker euro rather than operating performance, would be the main driver of the shares over the next six months.

Multinational companies typically report results in constant currency terms to give investors a clear idea of their underlying business performance. But they also break out the effect of currency fluctuations.